This is a continuation-in-part of my co-pending application U.S. Ser. No. 06/657,185 for Stale Air Detection for Dwellings, which is incorporated herein in its entirety by reference.
In that application ionization type detectors are employed to detect when oxygen levels in air fall below safe levels. A system for comparing air to be monitored as sensed by one detector with air of known quality as a reference as sensed by another detector provides a high sensitivity for reading very small variations of air contaminants.
One particular contaminant is of significant interest, namely radon gas, which is released from the soil and tends to accumulate inside houses at levels providing the risk of lung cancer comparable to that of heavy smokers. The Environmental Protection Agency has established a maximum safe level for radon at 4 picocuries per liter of air. Conventional radon detectors are not very sensitive and are very expensive, so that it is difficult to measure contemporaneously and almost instantly the radon presence in a home. Typical gathering times for detected samples to be processed in laboratory type equipment are greater than one week. Thus, there is a significant need for an instrument that may be used substantially instantly in the home for detecting the presence of radon, particularly if inexpensive and reliable in calibration with a detection sensitivity down to the range of 4 picocuries per liter of air.
The system in the foregoing application is deficient in its capability to detect radon at the desired sensitivity to low radon levels so that for example the 4 picocuries per liter radon level can be accurately ascertained in an inexpensive and substantially instantaneous detection of the presence of radon in a dwelling. It is particularly desirable also to be able to sample the local air about a seam or water pipe coming through basement wall in a search for radon presence. Thus an objective of this present invention is to provide a sensitive and rapid air contamination portable detector that will detect in situ low levels or radon.